1. Field of the Invention
The present invention relates to an image processing method enabling an image corresponding to image data generated by various applications to be printed by a printer. More specifically, the invention relates to an image processing method for image data including a compressed image.
2. Description of the Related Art
With the digitalization of printing processing, Desktop Publishing (DTP) is rapidly expanding. With DTP, page layout are made by operations such as creating, processing, and editing of an image using various applications on processors such as personal computers or workstations. Film used for exposing a printing plate is generated on the basis of the page layout (image setter, RIP for plate), and a press plate for printing is generated by directly writing data to a printing plate, known as Computer to Plate.
In DTP, a separation process for separating an image of a page layout into colors of yellow (“Y”), magenta (“M”), cyan (“C”), and key (black or gray) (“K”) is performed, and a printing plate is exposed on the basis of the respective image data. Thus, a press plate is made having a printing plate on which a halftone image is made.
Prior to printing an image using an actual press plate, proof may be performed. In this case, a page layout is displayed on a monitor, or an image is printed out with a print device such as a laser printer or a page printer using a function such as WYSIWYG.
In applications for DTP, operations such as creating, processing, and editing of an image are performed to make a page layout by color. However, when a printing process using a press plate is performed, in order to make the machine plate, the page layout must be separated into ink components of colors, i.e., C, M, Y, and K.
Therefore, image data has to be color-separated into colors C, M, Y, and K with an application for DTP or an image processing apparatus, called Raster Image Processor (RIP), having functions for converting image data or drawing command into bit map data.
When a layout (page layout) is made by using DTP applications, high-resolution image data is used to obtain sufficient image quality on a printed matter. However, since the high-resolution image data has a large volume (image size), a lot of processing time is required to print out drawing data or image data on a page layout, and sending the data takes a lot of time as well.
As a method of solving these problems, various image replacing servers using low-resolution images in layout operations are proposed (e.g., see Japanese Patent Application Laid-Open (JP-A) Nos. 2000-341503 and 2000-341504).
However, in these proposals, high-resolution images must be registered in advance for replacement. When images are frequently modified, when the duration of use of an image is short, or when an image is used only once, registered images must be frequently managed. For this reason, management for images becomes troublesome.
In recent years, with the progress of image compression technology, increasing numbers of users utilize image compression. In addition, it has been determined that image data subjected to high-level compression such as JPEG format is useful, and such images are often applied to make a page layout.
However, when complex image data obtained by performing a compression process such as a JPEG process to image data exists on a page layout applied to color separation, color separation is not properly performed, and data consisting of only K-color data is obtained with respect to the image.
In other words, in a standard printer, a color image is handled without performing color separation. For this reason, color printing can be performed. In order to print using a machine plate, however, the image data must be separated into C, M, Y and K plate for process color printing. At this time, for image data that demands complex processes, only a K-color image is output.
In this manner, when a page layout is being made with a printer, or when proof printing of the made layout is performed, the resultant image looks like a color image. However, when a printing process using a machine plate is performed, an image using only the K color is made on the printed matter and the printed matter is unsatisfactory due to the occurrence of printing trouble. This adversely affects the quality of the printed image.